1. Field of the Invention
The invention relates generally to generators and, more particularly, to a generator inspection system capable of inspecting the components of relatively small to medium size generators, with the rotor of the generator in situ.
2. Background Information
Electrical generators are available in a range of sizes depending on the power output required for the particular application in which the generator will be employed. All generators must be routinely inspected, regardless of size, in order to, among other things, determine the integrity of the stator and the rotor, and to ensure that the performance of the generator will not be compromised in any way.
By way of example, two undesirable conditions for which generators are commonly inspected include the degradation of the insulation between the stator laminations, which can lead to shorts, and the loosening of the stator coil wedges, which are located within the slots defined by the stator and prevent the stator coils from vibrating. Defects in the insulation between stator laminations result in the formation of a conductive path through which current is induced. These damaged regions become hot spots which, if not addressed, can cause damage to adjacent insulation and iron melting. Traditionally, manual tests were performed to inspect for such conditions, wherein the rotor was removed from within the stator. Rotor removal is time-consuming and can lead to damage to the stator. The process of removing the rotor, manually performing the test, and replacing the rotor can consume several days, resulting in an extended generator downtime that imposes serious problems for those relying on operation of the generator.
More recently, generator inspection systems have been developed which are capable of inspecting the generator, for example, by conducting a visual inspection with the rotor in situ. More specifically, as disclosed, for example in U.S. Pat. No. 6,814,169, self-propelled remote-controlled inspection vehicles are known to be employed to perform a number of tasks in locations which are generally inaccessible to humans including, for example, various locations within electrical generators. Generally, such systems include a remote-controlled carriage consisting of a propulsion frame and a platform attached to the frame. The platform is structured to carry a plurality of different interchangeable accessories (i.e., inspection equipment such as cameras and sensors, and electric motors). See also, U.S. Pat. Nos. 4,803,563; 4,889,000; 4,962,660; 4,970,890; 5,020,234; and 5,365,166.
FIGS. 1 and 2 show one example of an inspection system 2 used to inspect relatively large (e.g., about 100 Megawatts or more) generators, such as the turbine generator 4, which is partially shown. The system 2 includes a computer and video system 6 connected via cables 8,10 to carriage 12. The carriage 12 is movably mounted on an indexer plate assembly 14. A tangential drive motor 16 drives the carriage 12 to the desired lateral position between the rotor 18 and stator 20. In FIGS. 1 and 2, the carriage 12 is shown engaged with teeth 22 of stator 20. Coil 24 is mounted between stator teeth 22 and includes laminates 25. A single indexer assembly 26 is coupled at or about one end of the generator rotor 18 and includes sprockets 28 (best shown in FIG. 2). The indexer assembly 26 rides on chains 30 to move the indexer plate assembly 14 around the circumference of the rotor 18, along retaining ring 32. Once positioned at the desired location, the carriage 12 is unilaterally inserted and withdrawn from only one end of the generator rotor 18, where the single indexer assembly 26 is mounted. Electrical, video and control signals are transmitted to and from the computer and video system 6 (FIG. 1) to indexer 26 and carriage 12 via the cables 8,10 (FIG. 1).
Although this approach has worked reasonably well for such large generators where the minimum passage (e.g., without limitation, the air gap between the rotor and stator) through which the inspection vehicle or carriage must pass is typically greater than about 0.75 inches (1.91 centimeters), the relatively bulky nature of the configuration and required components (e.g., without limitation, internal motors and self-propelling drive components) of known remote-controlled inspection vehicles generally inhibits their ability to pass through smaller openings (i.e., less than about 0.75 inches (1.91 centimeters) and thus to inspect smaller generator units (i.e., less than about 100 Megawatts), without first requiring the disassembly of the generator. In addition to the small passages within relatively small generators, the general configuration of such generators includes, for example, bends, offsets, and other locations which must be inspected but which cannot accommodate the aforementioned inspection equipment. It is difficult for proper alignment to be achieved and maintained with respect to such small generators with the carriage 12 being inserted and withdrawn from the single indexer assembly 26 mounted at only one end of the generator rotor 18.
There is a need, therefore, for an inspection system capable of effectively inspecting generators, such as relatively small (i.e., less than about 100 Megawatts) generators, without first requiring disassembly thereof.
There is, therefore, room for improvement in generator inspection systems.